According to Associate Press, the gunman who killed five police officers at a protest march received training from a private self-defense school in Texas, a school official said Saturday at the academy that teaches firearm tactics, including “shooting on the move,” a maneuver in which an attacker fires and changes position before firing again.

Micah Johnson, an Army veteran, received instruction at the Academy of Combative Warrior Arts in the Dallas suburb of Richardson about two years ago, a person who said he was in charge of the organization told The Associated Press. The man refused to answer additional questions and would not give his name.

The man’s statement was corroborated by a police report from May 8, 2015, when someone at a business a short distance away called in a report of several suspicious people in a parked SUV.

The investigating officer closed the case just minutes after arriving at the scene in a parking lot behind a strip mall. While there, the officer spoke to Johnson, who said he “had just gotten out of a class at a nearby self-defense school.”

Johnson told the officer he was “waiting for his dad to arrive” and pick up his brother. No one else was apparently questioned.

On Friday, Dallas Mayor Mike Rawlings described Johnson as “a mobile shooter” who had written manifestos on how to “shoot and move — and he did that.”

The academy website refers to one of its courses as a “tactical applications program,” or TAP.

“Reality is highly dynamic, you will be drawing your firearm, moving, shooting on the move, fixing malfunctions, etc. all under high levels of stress,” the website says. “Most people never get to train these skills as they are not typically allowed on the static gun range.”

The TAP training includes “shooting from different positions,” ”drawing under stress” and “drawing from concealment.”

People could be seen training Saturday at the school in a nondescript shopping center, but the doors were locked.

When asked about Johnson, a man who answered the door said, “He trained two years ago. … I don’t know anything about Micah. I’m sorry. He’s gone. He’s old to us. I have thousands of people.”

A neighbor reported to investigators that Johnson had been seen practicing some sort of military drill in his backyard in the Dallas suburb of Mesquite, said Clay Jenkins, the Dallas County judge, the county’s most senior elected official.

Tensions were still high Saturday in Dallas, where 20 square blocks of downtown remained cordoned off as a crime scene. The police department tightened security Saturday evening after receiving an anonymous threat. Officers in helmets carrying rifles were stationed outside at least two buildings.

Earlier in the day, President Barack Obama called Johnson a “demented individual” who does not represent black Americans any more than a white man accused of killing blacks at a church in Charleston, South Carolina, represents whites.

“So we cannot let the actions of a few define all of us,” Obama said from Warsaw, Poland, where he attended a NATO summit.

The president planned to visit Dallas in a few days and to convene a White House meeting next week with police officers and community and civil rights activists.

It was the third time in as many days that Obama has spoken about the fatal police shootings of black men in Louisiana and Minnesota that were immediately followed by the sniper attack in Dallas.

Johnson donned a protective vest and used a military-style semi-automatic rifle, officials said.

He was killed by a robot-delivered bomb Thursday after the shootings, which marked the deadliest day for U.S. law enforcement since the Sept. 11, 2001, terrorist attacks.

In all, 12 officers were shot just a few blocks from where President John F. Kennedy was slain in 1963.

The 25-year-old gunman had amassed a personal arsenal at his home, including bomb-making materials, rifles, ammunition and a journal of combat tactics, authorities said Friday.

He followed black militant groups on social media, including one that posted a message Wednesday encouraging violence against police.

Johnson was a private first class with a specialty in carpentry and masonry. He served in the Army Reserve for six years starting in 2009 and did one tour in Afghanistan from November 2013 to July 2014, the military said.

The attack began Thursday evening while hundreds of people were gathered to protest the police killings of Philando Castile, who was fatally shot near St. Paul, Minnesota, and Alton Sterling, who was shot in Louisiana after being pinned to the pavement by two white officers.

Video showed protesters marching along a downtown street about half a mile from City Hall when shots erupted and the crowd scattered, seeking cover.

Marcus Carter, 33, was in the area when people started running toward him, yelling about gunshots. Carter said the first shot sounded like a firecracker. But then they proceeded in quick succession, with brief pauses between spurts of gunfire.

“It was breaks in the fire,” he said. “It was a single shot and then after that single shot, it was a brief pause,” followed by many shots in quick succession.

After shooting at the Dallas officers, Johnson tried to take refuge in a parking garage and exchanged gunfire with police, authorities said.

During negotiations, he said he wanted to exterminate whites, “especially white officers,” the police chief said.

Elsewhere in Texas, police shot and killed a man early Saturday after he was spotted standing in a Houston road with a revolver. Authorities said officers told the man to put down the weapon, but he instead pointed it in the air, then at the police.